Process for selectively hydrogenating mixed phase front end C2-C10 greater unsaturated hydrocarbons

Abstract

The present invention provides a process for selectively hydrogenating C 2 -C 10 greater unsaturated hydrocarbons (acetylenes and diolefins) at the upstream side of a front depropanizer or front deethanizer in an olefin production plant. After passing through a mixed phase hydrogenation reactor to selectively hydrogenate, the olefin plant process stream passes to a front depropanizer or front deethanizer. The process according to the present invention is able to selectively hydrogenate C 2 -C 10 greater unsaturated hydrocarbons (including acetylene), to reduce the number of equipments, the amount of equipment fouling and the energy consumption.

1. A process for selectively hydrogenating C 2 -C 10  acetylenes and diolefins in an olefin production plant comprising the steps of, in sequence
 (1) passing an olefin plant feed stream through a mixed phase hydrogenation reactor [ 24 ] to mixed phase-hydrogenate at least a portion of the C 2 -C 10  acetylenes and diolefins;  
 (2) passing the effluent from the mixed phase hydrogenation reactor [ 24 ] through a front depropanizer [ 27 ] to separate into a vapor stream rich in C 3  and lighter components and a liquid stream rich in C 4  and heavier components; or passing the effluent from the mixed phase hydrogenation reactor [ 24 ] through a front deethanizer [ 27 ] to separate into a vapor stream rich in C 2  and lighter components and a liquid stream rich in C 3  and heavier components;  
 (3) passing the vapor stream from step (2) through the vapor phase hydrogenation reactor [ 33 ] to vapor phase hydrogenate; recycling a portion of a C 4 -C 10  process stream to the mixed phase hydrogenation reactor [ 24 ], and passing the other portion to the downstream separation zones; and  
 (4) passing the effluent from the vapor phase hydrogenation reactor [ 33 ] to further separation zones.  
 
     
     
       2. A process as claimed in  claim 1 , wherein said olefin plant feed stream is derived from a process stream of a steam pyrolysis facility or a catalytic cracking facility. 
     
     
       3. A process as claimed in  claim 1 , wherein said olefin plant feed stream comprises a component selected from the group consisting of hydrogen, methane, carbon monoxide, acetylene, ethylene, ethane, propylene, propane, propyne, propadiene, butene, butyne, 1,3-butadiene, butane, C 5  nonaromatics, C 6  nonaromatics, C 7  nonaromatics, C 8  nonaromatics, benzene, toluene, styrene, and mixtures thereof. 
     
     
       4. A process as claimed in  claim 1 , wherein said front depropanizer [ 27 ] or front deethanizer [ 27 ] operates at a pressure ranging from 0.5 MPa to 4.0 MPa. 
     
     
       5. A process as claimed in  claim 1 , wherein said mixed phase hydrogenation reactor operates at a temperature from 10° C. to 90° C. and a pressure of from 0.7 MPa to 4.0 MPa, in the presence of a mixed phase hydrogenation catalyst comprising Group VIII metal or Group IB metal. 
     
     
       6. A process as claimed in  claim 5 , wherein said mixed phase hydrogenation catalyst comprises one or more components selected from the group consisting of Palladium, Ruthenium, Platinum, and Nickel arsenide that is carried on a support and the support is selected from the group consisting of titanium oxide, silicon oxide, aluminum oxide, zinc oxide, tin oxide, molecular sieve, and mixtures thereof. 
     
     
       7. A process as claimed in  claim 6 , wherein said mixed phase hydrogenation catalyst also includes a promotor selected from the group consisting of potassium, sodium, lithium, calcium, magnesium, barium, copper, silver, gold, zinc, lanthanum, cerium, molybdenum, tungsten, antimony, arsenic, bismuth, vanadium, and the mixtures thereof. 
     
     
       8. A process as claimed in  claim 1 , characterized in that recycling a portion of the liquid stream of step (2) to the mixed phase hydrogenation reactor [ 24 ], and passing the other portion to debutanizer or depropanizer. 
     
     
       9. A process as claimed in  claim 1 , wherein said vapor phase hydrogenation reactor operates at a temperature from 30° C. to 200° C. and a pressure of from 0.6 MPa to 4.0 MPa, in the presence of a Group VIII metal-containing hydrogenation catalyst. 
     
     
       10. A process as claimed in  claim 9 , wherein said vapor phase hydrogenation catalyst contains one or more components selected from the group consisting of palladium, ruthenium, platinum and nickel arsenide that is carried on a support and the support is selected from the group consisting of titanium oxide, silicon oxide, aluminum oxide, zinc oxide, tin oxide, molecular sieve and the mixtures thereof. 
     
     
       11. A process as claimed in  claim 1 , wherein said vapor phase hydrogenation catalyst further includes a promotor selected from the group consisting of potassium, sodium, lithium, calcium, magnesium, barium, copper, silver, gold, zinc, lanthanum, cerium, molybdenum, tungsten, antimony, arsenic, bismuth, vanadium, and the mixtures thereof. 
     
     
       12. A process as claimed in  claim 1 , wherein said further separation zones include demethanizer, deethanizer and the separation zone of the mixtures thereof. 
     
     
       13. A process for selectively hydrogenating C 2 -C 10  greater unsaturated hydrocarbons in an olefin production plant comprising the following steps:
 a. passing an olefin-containing feed stream through a heat exchanger [ 23 ], to cool said feed stream to 10-90° C.;  
 b. passing the process stream from step (a) through the mixed phase hydrogenation reactor [ 24 ];  
 c. Selectively hydrogenating at least a portion of the greater unsaturated hydrocarbons in the process stream entering the mixed phase hydrogenation reactor [ 24 ];  
 d. passing the effluent from the mixed phase hydrogenation reactor [ 24 ] in step [c], through coolers [ 25 ], [ 26 ] to cool said effluent;  
 e. passing the cooled process stream through the front depropanizer [ 27 ], to separate into a vapor stream rich in C 3  and lighter components, and a liquid stream rich in C 4  and heavier components, front depropanizer [ 27 ] operating at a pressure ranging from 0.5 MPa to 2.0 MPa; or passing the cooled process stream through front deethanizer [ 27 ], to separate into a vapor stream rich in C 2  and lighter components, and a liquid stream rich in C 3  and heavier components, the front deethanizer [ 27 ] operating at a pressure ranging from 2.5 MPa to 4.0 MPa;  
 f. passing the vapor phase rich in C 3  and lighter components through the vapor phase hydrogenation reactor [ 33 ], to selectively hydrogenate all the residual acetylene, propyne, propadiene; or passing the vapor phase rich in C 2  and lighter components through the vapor phase hydrogenation reactor [ 33 ], to selectively hydrogenate the residual acetylene; recycling a portion of the liquid stream to mixed phase hydrogenation reactor [ 24 ], the other portion to debutanizer or depropanizer;  
 g. cooling and partially condensing the vapor phase process stream from the vapor phase hydrogenation reactor, and recycling the condensed process stream as reflux liquid to the top of the front depropanizer [ 27 ] or the front deethanizer [ 27 ];  
 h. passing the vapor phase stream from step (g) to the downstream separation zones for the removal of methane, ethane, or the mixtures thereof.